hensler



Oct. 16, 1962 E. e. HENSLER 3,058,874

METHOD FOR FORMING SHORT RADIUS FIBRE BENDS Filed Feb. 20, 1959 3 Sheets-Sheet 1 llVVf/VIFA EZmef 6. Hensler "TU 15d.

JTTGRNEY 1962 E. G. HENSLER 3,058,874

METHOD FOR FORMING SHORT RADIUS FIBRE BENDS Filed Feb. 20, 1959 s Sheets-Shet 2 1962 E G. HENSLER 3,058,874

METHOD FOR FORMING SHORT RADIUS FIBRE BENDS Filed Feb. 20, 1959 5 Sheets-Sheet 5 J I Md INVf/Vfdk a 4 Elmer 6. fiensler segment of a tube are United States Patent 3,058,874 NETHOD FUR FGRMING SHORT RADIUS FERE BENDS Elmer G. Hensler, Barton, Wis., assignor to McGraW- Edison Company, Miiwaukee, Wis., a corporation of Delaware Filed Feb. 29, 1959, Ser. No. 794,744 7 Claims. (Q1. 162223) This invention relates in general to a method for forming short radius fibre bends, and more particularly to a method for forming short radius fibre bends adapted to later impregnation with a suitable saturant such as coal tar pitch and the like.

In recent years there has been a tremendous expansion in the use of tubular conduit and pipe formed of bulk fibre. In straight stock length, the material is well adapted for fast production by mass production techniques and when saturated with a suitable saturant such as coal tar pitch and the like has good durability and use.

Much of the manufacture of various shaped components has heretofore been done by hand operation. Various shaped components have also been made from other materials. Utilization of these components in applications governed by installation material codes has in some cases been refused in the interest of uniformity in the over-a l installation. Therefore for purposes of uniformity, a pitch-fibre short radius elbow is very desirable.

The instant method for forming short radius fibre bends is an improvement on the method shown in application having Serial No. 732,704, filed May 2, 1958, as invented by F. B. Burns and E. M. Johnson and assigned to the same assignee. This application has matured into Patent No. 2,998,985, issuing September 5, 1961.

In the aforementioned application of Burns and Johnson, certain problems were encountered in adapting same to mass manufacturing techniques. Generally speaking, these problems involved a considerable amount of wastage, a very rough end surface for presentation to the tapering machine, a tendency for the elbow to ovalize during the forming operation and a non-uniform wall thickness after the taper is placed on the elbow due to the curvature of the end portion.

It is an object of this invention to provide a process for forming short radius fibre bends which requires exceedingly little wastage in the manufacturing operations and allows the tubes to be precut to their final dimension prior to the forming operation.

It is a further object of this invention to provide a process as above set forth which affords short radius bends which have non-ovalized end portions and which are in true round in cross-section.

It is a further object of this invention to provide a process wherein the end portions of a short radius toroidal offset from and tangential to the toroidal segment so as to provide a straight end portion at each end of the short radius bend.

It is a further object of this invention to provide a process which afiords smooth exterior end portions of the formed toroidal section for easy presentation of the said end portions to a tapering machine.

It is a further object of this invention to provide a method which affords a uniform wall thickness at the tapered ends of the toroidal section short radius bend for uniform joint connections with other sections of fibrous articles as suitable and desired.

It is a further object of this invention to provide a. method utilizing a beveled collar which afiords a smooth transition from the end portions to the compressed prestressed portions of the toroidal segment short radius bends.

It is a further object of this invention to provide a process which is well adapted to mass manufacture techniques for providing uniform short radius fibre bends which meet governmental standards and are otherwise well adapted for the purposes for which they are designed.

The novel features that are characteristic of this invention are set forth with particularity in the appended claims. The invention, itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof will best be understood by the following description of specific embodiments when read in connection with the accompanying drawings in which:

FIG. 1 is a view, partially in section, of a pre-cut wet fibre tube prior to any work thereon;

FIG. 2 is a View of the tube shown in FIG. 1 undergoing a prestressing operation;

FIG. 3 is a sectional View through the tube subsequent to the prestressing operation showing a relative disposition of the prestressing marks on the circumferential periphery of the tube;

FIG. 4 is a semidiagrammatie view, partially in section, of an apparatus for forming the short radius fibre bend;

FIG. 5 is an end view of the apparatus shown in FIG. 4, the dotted lines showing the position of a portion of the apparatus during the loading and unloading stages of the process;

FIG. 6 is a perspective view of the collars used during the forming operation;

FIG. 6a is an enlarged fragmentary sectional view of the collars, fibre tube, and mandrel when the tube is loaded on the straight mandrel portion of the forming apparatus;

FIG. 6b is a FIG. 6a showing the disposition of fibre tube is on the curved mandrel;

FIG. 7 is a view similar to FIG. 4 showing the relative position of the parts just after the tube has been formed into a short radius bend on the forming apparatus;

FIG. 8 is a cross sectional view of a wet fibre tube on a mandrel showing the ovalizing tendency of the tube that occurs when no collars are employed in the forming operation;

FIG. 9 is a plan view of a straightening form for realigning the end portion of the short radius fibre bend after it has been removed from the curved mandrel of: the forming apparatus;

FIG. 9a is a sectional FIG. 9;

FIG. 10 is a top view of a drying form employed for retaining short radius fibre bends in the desired shape during the drying operation;

FIG. 11 is a perspective view of the drying form of FIG. 10 after it has been inserted into a recently formed short radius fibre bend preparatory to drying;

FIG. 12 is a semidiagrammatic view of the operation showing the short radius bends being dried in a drying oven;

FIG. 13 is a semidiagrammatic view of the impregnation step in the manufacture of short radius fibre bends;

FIG. 14 is a plan view of the finished short radius fibre bend article after the tapering operation; and,

FIG. 14:: is an end View along lines l4a-l4 a of FIG. 14.

In the manufacture of short radius fibre bends, an elongated tube 20 may be formed of cellulose material on a standard forming machine, and a plurality of laminaes is convolutely rolled to a wall thickness which is standard for the straight stock pipe for conduit for which the finished product is to be associated. The tube, after being fragmentary sectional view similar to the parts when the view along lines 9a-9a of rolled, becomes substantially a seamless homogeneous mass and the interlaminar bonds approach the intralaminar bonds. The water content of this wet fibrous tube 20 is. preferably that of the normal .value. made on the forming machine for use in the manufacturerof straight stock fibre pipe or conduit. (It is to be noted that it is of considerable value to use a standard tube as a starting point for the short radius bends as this doesnot require a modification of existent production machinery or techniques.)

As shown in FIG. 1, the wet tube 20 may be cut to its finished length and subjected to a prestressing operation shown in FIG. 2. This prestressing operation shown is one of any number of techniques to be used in prestressing the outer portion of the tube 20 and the method here employed is the rolling of the tube on a form having upset portions 21. The upset portions 21 are made by placing a plurality of wires on a metal sheet, the wires being parallel and spaced at approximately three-quarter inch intervals. This spacing will vary from the tube to tube depending upon the diameter of the tube being formed. It will be noted thatthe length of the wires 21 is such that only approximately 290 of the periphery is formed with the indentations 23, whereas the top portion of the tube (approximately 70) 24 does not have the prestressing marks thereon. For more detailed explanationof the prestressing operation, reference is to be had to the afore mentioned Burns and Johnson application assigned to the same assignee. It will be further noted that the two end portions of the tube are not prestressed for reasons hereinafter appearing. This lack of prestressing at the end portion differs from the aforementioned Burns and Johnson teachings.

After the tube has been prestressed, it 'is preferably placed on a'suitable forming machine 25 having a straight mandrel portion 26 and a detachable curved mandrel portion 27. The interiors of both of these mandrels is preferably heated by heat source 30 through appropriate conduits 31 and 32, said heat source and conduits being here shown semidiagrammatically. The mandrels 26-27 are preferably heated to a temperature affording a cushion of steam for freeing the tube 20 for movement along the mandrel. It will be noted in the FIG. 4 that the curved mandrel is here shown as pivotally mounted at 28 for ingress of the straight tube 20 onto mandrel 26 and egress of the formed tube 20a from mandrel 27. Suitable latching means 29 is provided for aligning the straightmandrel 26 and curved mandrel 27 and is employed at the juncture of the two mandrels. Drive means 33, here shown in the form of semidiagrammatic air cylinder 34 which is attached to a drive collar 35, affords axial movement of the engaging collar 36 along the straight mandrel 26 to move the tube thereal ong to the curved mandrel 27. Engaging cdllar 36 is pivotally linked to the drive collar 35 by suitable strap means 3 i An essential departure from the method and apparatus taught by Burns and Johnson aforementioned is the use of a metal collar means 38 best shown in perspective view FIG. 6. The collar is essentially two split halves which are hinged at 40 and are fastened by suitable fastening means 41 at the topportion'thereof. One interior edge surface of the metal col'lar is preferably tapered as shown at 39.

The collars 38 are adapted to be disposed about the leading and trailing non-prestressed end portions of the tube 20 after it has been disposed on the straight mandrel 26. The beveled portions in each case being on the inboard sides (facing each other) as shown in FIG. 4. FIG. 6a shows an enlarged fragmentary sectional view of the collar 38 disposed about the trailing end portion of the tube 20 and there'lative position of the taper 39. The collar 38, as here shown, is approximately 2 /2 inches 'in axial length and the non-tapered end surface thereof is preferably disposed just flush'with the end of the tube 20. The Qbverse applies to the leading end'portion; It

of the formed bend.

4 will be noted that the first prestressing mark 23 is beyond the collars 38.

The collars 38 serve a plurality of purposes. They prevent ovalizing of the leading and trailing end portions of tube 20 in cross sectional direction when the tube is forced onto the curved mandrel 27, said ovalizing being shown bydimension 41 in FIG. 8 which pictorially illustrates what occurs when no collars 38 are used. The ovalizing of the tube occurs on the outer radius of the tube when it is forced onto the curved mandrel since there is a tendency for the top portion of the leading and trailing edges to continue in a straight line unless counteracted by the collars 38. The Burns and Johnson garter as taught in the aforementioned application was for prevention of end splitting and did not pertain to the counteracting of the ovalizing tendency. Further, the formed tube of Burns and Johnson taught the removal of the end portions of the tube prior to tapering to overcome the ovalized end portions, such a procedure being wasteful. As aforementioned, the tube 20 is so formed with end portions having no compression marks in this area of the tube. The interior of the collars 38 are smooth and maintain a smooth end portion outer peripheral surface on the ends of the tube for later presentation of the end portions to the tapering machine;

*It will be further noted, as shown in FIG. 6b, that there is a slight indentation on the lower side of the tube 20a where it engages the beveled portion 39 of the collar 38. This decreased wall thickness at this point appears to alleviate itself due to the inherent elasticity of the fibrous particles and the tube tends to regain its curvilinear shape at this point. Further, the taper or bevel 39 tends to provide a gradual transition from the thicker center portion of the formed tubes to the uniform and slightly thinner end portions'of the tube.

After the air cydlinder has been operated to move the fibre tube 20 quickly along the heated mandrel 26 and onto the curved mandrel 27, a short radius bend 20a is formed having spaced regular compression crease marks on the center portions and no marks on the end portions. The bend is then removed from the curved mandrel 27. The collars 38 are then removed and the short radius bend is inserted into the realigning form 43 shown in FIGS. 9 and 9a. The form 43 may be made of plastic, wood, or any other suitable material, the preferred material being :fibre glass. The central portion 46 of the form 43 is formed to the same radius of the toroidal segments, i.e. identical in curvature to curved mandrel 27. It is important to note that the form 43 is formed with straightened end portions 44 having an axial dimension about equivalent to the length of the collars 38 and which are offset from the curvature of the center portions and in alignment with center lines 45 which are tangential to the center line of portion 46. Thusthe bend 20a after being removed from the forming machine so realigned in the realigning form 43 to have theend portions straightened by the straight portions 44 of form 43. Suitable marks 47 may be made in the form 43 to indicate the disposition of the end surfaces of the bends 2011 when it is placed in the form. Of course, if desired, the form 43 may be made only as long'as marks 47 if that is desired. I I

After disposition of the wet formed tube in the form 43, andrealigning same, a drying form 48 shown in FIG. 10 is associated with the bend 20a as shown in perspective view, FIG. 11. The drying form 47- comprises a pair of end plugs 50 having closed ends 51 with through-bolts 49 for connection of the arms 52 one to the other by suitable fastening means 53. It will be noted that the center line of the plugs 50 are the same center line dimension 45 shown relative to the realignment form 43 in FIG. 9 to maintain the realigned shape It will be further noted that the plugs 50 with the closed ends 51 prevent the ingress and egress of air and moisture through the tube during the drying operation which has been found to substantially aid in even drying of the bends 20a.

As shown in FIG. 12, the bends 20a with the drying forms 48 therewithin are disposed within a suitable oven 54 and dried until the moisture content is reduced to an appropriate low level, all in accordance with standard procedures in the art.

Subsequent to drying of the bends and removal from the oven, the drying forms 48 are removed and the bends 2011 are disposed in a suitable pitch Vat 55 filled with a suitable coal tar pitch 56 under standard vacuum impregnating techniques, all as well known and understood in the art. This is shown semidiagrammatically in FIG. 13.

FIGS. 14 and 14a show the finished short radius bend 20b, the end portions 60 having been tapered at 58 by a suitable machine. The tapering operation and result is considerably enhanced because the collars afford the very smooth character of the outer periphery of the straight end portions 60 of the bend. Further, a uniform end wall thickness, as shown at 59, is provided because the end portions 60 are realigned from the curved relationship and thus one portion of the wall thickness 59 is not thicker at the inner radius than at the outer radius as happens in the Burns and Johnson techniques. Also, very little wastage, shown at 57, is encountered by this entire operation since the only removal of stock is that amount lost in the tapering operation, since the end portions of the tube are directly usable in the finished product.

Although specific method and apparatus and article have been shown and described, it is with full awareness that many modifications thereof are possible. The invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended calims.

I claim:

1. The method of fabricating a curved fibre tube comprising pushing a preformed substantially straight hollow tube of wet fibrous material having front and rear end portions along a path surrounding a curved projection of its axis while confining the interior surface of said tube against radial contraction and confining only the front and rear end portions of the exterior surface of said tube against radial expansion, heating the surface of the path adjacent the interior of the tube to provide a cushion of steam therebetween and drying the tube with a form for retaining for a major portion of the tube a curvature conforming to said curved projection to impart a self-sustaining set to the tube.

2. The method of fabricating a curved fibre tube comprising pushing a preformed substantially straight hollow tube of wet fibrous material having front and rear end portions and a central portion having spaced indentations on at least a portion of external surface thereof along a mandrel path surrounding a curved projection of its axis while confining the interior surface of said tube against radial contraction, and confining the said end portions only of the exterior surface of said tube against radial expansion to provide compressive crease marks on said external surface of said central portion at the points of said spaced indentations, heating the surface of the path adjacent the interior of the tube to provide a cushion of steam therebetween and drying the tube on a form for retaining for said central portion a curvature conforming to said curved projection to impart a selfsustaining set to the tube.

3. The method of claim 2 including the step of removing the tube from the mandrel prior to drying and realigning the front and rear end portions thereof in a path tangential to the curved projection of its axis.

4. A method of manufacture of short radius bends from elongate wet tubes of fibrous material comprising disposing said tube upon a mandel having a curved portion, freeing said tube for movement along said mandrel, disposing said tube on the curved mandrel portion, removing the tube from the curved mandrel, restraightening only the curved end portions of the bent tube, associating the straightened end portion and curved center portions with a drying form and disposing the tube in a drying oven to impart a self-sustaining set to the tube, impregnating the bent dried tube and machining the bent tube to its final desired dimension.

5. A method of manufacture of short radius bends from elongate set tubes of fibrous material having front and rear end portions and a center portion comprising applying spaced prestressing compressive forces to cause parallel indentations on at least a portion of the outer surface of only the center portion of the tube, said indentations being substantially normal to the long axis of the tube, disposing said tube upon a mandrel having a curved portion, freeing said tube for movement along said mandrel, disposing said tube on the curved mandrel portion to procure a bent tube having compression creases only at said spaced substantially parallel indentations on the outer surface of the tube.

6. The method of claim 5 including the step of placing short restraining collars about the outer periphery of the front and rear end portions of the tube prior to movement of the tube to the curved mandrel.

7. The method of fabricating a curved fibre tube comprising pushing a preformed substantially straight hollow tube of wet fibrous material having front and rear end portions along a path surrounding a curved projection of its axis while confining the interior surface of said tube against radial contraction and confining only the front and rear portions of the exterior surface of said tube against radial expansion, freeing the tube for movement along said curved projection of its axis and drying the tube with a form for retaining for a major portion of the tube a curvature conforming to said curved projection to impart a self-sustaining set to the tube.

References Cited in the file of this patent UNITED STATES PATENTS 43,130 Perry June 14, 1864 46,934 Perry Mar. 21, 1865 553,674 Greenfield Jan. 28, 1896 1,598,893 Taylor Sept. 7, 1926 1,880,053 Shur et al. Sept. 27, 1932 2,057,916 Quartz et al. Oct. 20, 1936 2,316,700 Maltby Apr. 13, 1943 2,327,347 Gibbin Aug. 24, 1943 2,389,038 German Nov. 13, 1945 2,802,404 Taylor Aug. 13, 1957 

7. THE METHOD OF FABRICATING A CURVED FIBRE TUBE COMPRISING PUSHING A PREFORMED SUBSTANTIALLY STRAIGHT HOLLOW TUBE OF WET FIBROUS MATERIAL HAVING FRONT AND REAR END PORTIONS ALONG A PATH SURROUNDING A CURVED PROJECTION OF ITS AXIS WHILE CONFINING THE INTERIOR SURFACE OF SAID TUBE AGAINST RADICAL CONTRACTION AND CONFINING ONLY THE FRONT AND REAR PORTIONS OF THE EXTERIOR SURFACE OF SAID TUBE AGAINST RADIAL EXPANSION, FREEING THE TUBE FOR MOVEMENTT ALONG SAID CURVED PROJECTION OF ITS AXIS AND DRYING THE TUBE WITH A FORM FOR RETAINING FOR A MAJOR PORTION OF THE TUBE A CURVATURE CONFORMING TO SAID CURVED PROJECTION TOO IMPART A SELF-SUSTAINING SET TO THE TUBE. 